BERLIN, May 17 (Reuters) - The planned Nord Stream 2 gas pipeline from Russia to Germany raises U.S. intelligence and military concerns since it would allow Moscow to place new listening and monitoring technology in the Baltic Sea, an U.S. official said on Thursday.

Sandra Oudkirk, U.S. Deputy Assistant Secretary of State for Energy Diplomacy, told reporters in Berlin that Washington viewed the pipeline project as a bad choice, adding the U.S. was skeptical whether Russian transit guarantees for other countries such as Ukraine were enforceable.

A consortium of western companies and Russia’s Gazprom that is due to build the controversial subsea Nord Stream 2 gas pipeline to Germany said on Tuesday it was starting preparatory work in the Greifswald bay off Germany’s Baltic coast. (Reporting by Andrea Shalal Writing by Michael Nienaber Editing by Madeline Chambers)